Journal
MOLECULAR ECOLOGY
Volume 21, Issue 6, Pages 1453-1476Publisher
WILEY
DOI: 10.1111/j.1365-294X.2011.05398.x
Keywords
array comparative genome hybridization; biological control; heritability; multilocus sequence typing; non-Mendelian segregation; vegetative compatibility group
Funding
- North Carolina Cooperative State Research, Education and Extension Service [2008-34500-19396]
- National Research Initiative of the USDA Cooperative State Research, Education and Extension Service [2005-35319-16126]
- USDA
- National Science Foundation [1046167]
- Division Of Environmental Biology
- Direct For Biological Sciences [1046167] Funding Source: National Science Foundation
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Aspergillus flavus is the major producer of carcinogenic aflatoxins (AFs) in crops worldwide. Natural populations of A.similar to flavus show tremendous variation in AF production, some of which can be attributed to environmental conditions, differential regulation of the AF biosynthetic pathway and deletions or loss-of-function mutations in the AF gene cluster. Understanding the evolutionary processes that generate genetic diversity in A.similar to flavus may also explain quantitative differences in aflatoxigenicity. Several population studies using multilocus genealogical approaches provide indirect evidence of recombination in the genome and specifically in the AF gene cluster. More recently, A.similar to flavus has been shown to be functionally heterothallic and capable of sexual reproduction in laboratory crosses. In the present study, we characterize the progeny from nine A.similar to flavus crosses using toxin phenotype assays, DNA sequence-based markers and array comparative genome hybridization. We show high AF heritability linked to genetic variation in the AF gene cluster, as well as recombination through the independent assortment of chromosomes and through crossing over within the AF cluster that coincides with inferred recombination blocks and hotspots in natural populations. Moreover, the vertical transmission of cryptic alleles indicates that while an A.similar to flavus deletion strain is predominantly homokaryotic, it may harbour AF cluster genes at a low copy number. Results from experimental matings indicate that sexual recombination is driving genetic and functional hyperdiversity in A.similar to flavus. The results of this study have significant implications for managing AF contamination of crops and for improving biocontrol strategies using nonaflatoxigenic strains of A.similar to flavus.
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